By Jay Landers

Beginning in 2019, multiple retail water providers in Orange County, California, elected to shut down several dozen groundwater wells because they were found to contain low levels of a class of contaminants known as perfluoroalkyl and polyfluoroalkyl substances. In a region that depends heavily on groundwater for its water supplies, the closures have proved expensive, as the affected water agencies have had to rely even more than they typically do on costly imported water from California’s State Water Project and the Colorado River.

Following an extensive study of various methods of removing PFAS from drinking water, the Orange County Water District recently began operations at the first of more than 30 planned PFAS treatment facilities. Buoyed by a large low-interest loan from the U.S. Environmental Protection Agency, the OCWD is moving ahead with its expedited program to design and construct the remaining treatment systems.

Closing wells

The substances collectively known as PFAS comprise a group of thousands of human-made chemicals used in industrial processes, firefighting activities, and myriad consumer products, including makeup, clothing, food packaging, furniture fabrics, stain repellents, and nonstick coatings on cookware.

The most frequently studied PFAS variants are perfluorooctanoic acid, perfluorooctane sulfonate, and perfluorobutane sulfonic acid. The EPA and California’s State Water Resources Control Board have warned that exposure to certain types of PFAS, including PFOA and PFOS, may lead to adverse health outcomes in humans.

The OCWD manages the sprawling groundwater basin that provides drinking water for much of northern and central Orange County, which extends from Anaheim in the north to Huntington Beach in the south. Although various investigations are ongoing to identify potential sources of PFAS to local groundwater, one likely source of PFAS is thought to be infiltration to the basin from the Santa Ana River, which itself receives the contaminants from stormwater and wastewater from communities upstream of Orange County. As has been happening in a growing number of water supplies around the country, sampling of Orange County’s groundwater has detected PFAS in certain areas in recent years.

In 2020, the State Water Resources Control Board tightened its already stringent limits for PFOA and PFOS in drinking water. Of the 19 retail water providers that rely on groundwater from the Orange County groundwater basin, 11 have had to shut down a total of nearly 60 wells because of PFAS contamination, says Chris Olsen, P.E., the director of engineering for the OCWD.

Reopening the wells

To return the closed wells to service, the OCWD entered into agreements with 10 of the water providers to design and construct treatment systems to remove PFAS from their groundwater supplies, Olsen says. The remaining provider, the city of Anaheim, is delivering its PFAS treatment system by means of the design-build process with oversight from the OCWD.

For its part, the district has set an ambitious time frame for wrapping up the design, permitting, and construction of all 35 of the PFAS treatment systems needed by the retail providers. “We’re planning on having them all completed within the next two to three years,” Olsen says.

To this end, the OCWD has hired six consulting engineering firms — Jacobs, Tetra Tech, CDM Smith, Kennedy Jenks, Stantec, and AECOM — to provide design and construction management services for the treatment systems. To date, the district’s board has approved $16 million for such services, Olsen says.

exterior of system
The city of Fullerton’s Kimberly Well 1A PFAS Treatment Plant treats up to 3,000 gal./minute by means of four vessels containing ion-exchange resin. (Photo by OCWD principal engineer Ben Smith, P.E.)

Addressing site constraints is a key concern during the design process. “The main challenge is real estate,” Olsen says. The treatment systems include approximately 16 ft tall vessels with diameters of 12 ft, he says. Each vessel “takes up a lot of space,” Olsen notes. Besides the vessels themselves, the treatment systems also include prefiltration units and other components as well as the associated piping. “The footprint is a pretty good size,” he says. “That is the biggest consideration.”

Financing the treatment

All told, capital expenses associated with the 35 separate treatment systems are expected to cost approximately $275 million, to be paid entirely by the OCWD, Olsen says. However, operations and maintenance costs will be split between the district and the retail providers. Under this arrangement, the OCWD and the retail providers each will pay O&M costs of up to $75 per acre-ft of treated water. Any costs exceeding this threshold will be paid by the retail provider. Ultimately, the treatment facilities may need to operate for 30 years, Olsen says.

In late August, the EPA awarded the district a $131 million loan through the agency’s Water Infrastructure Finance and Innovation Act program. The low-interest loan is expected to save the district on the order of $26 million as compared with traditional financing mechanisms, according to the EPA’s Aug. 25 news release announcing the loan.

The first of the PFAS treatment facilities went online in late June. The city of Fullerton’s Kimberly Well 1A PFAS Treatment Plant treats up to 3,000 gal./minute by means of four vessels containing ion-exchange resin, a type of media that adsorbs PFAS. Comprising two parallel treatment trains, the system is arranged in a lead-lag configuration, in which effluent from the first vessel undergoes further treatment in the second vessel, says Megan Plumlee, Ph.D., P.E., the research director for the OCWD. The filtered water then is disinfected before entering the city’s distribution system.

Testing adsorbents

The Kimberly Well 1A system is “performing as we expected,” Olsen says. “It’s providing treated water with no detectable levels of PFAS.” The treatment system employs PSR2+ ion-exchange resin from Evoqua Water Technologies LLC. This particular ion-exchange resin was selected based on pricing and its performance during pilot testing conducted by the OCWD, Olsen says.

In December 2019, the district, working with Jacobs, began what is believed to be the nation’s largest pilot test of PFAS treatment media. The study tested 14 different adsorbents at pilot scale: eight granular activated carbon systems, four ion-exchange resin systems, and two alternative media systems representing new types of adsorbents that had recently entered the market.

Each adsorbent was evaluated in terms of its efficacy and cost-effectiveness in removing PFAS from groundwater, which was fed to the pilot system from a district-owned well that contains PFAS at levels similar to other local wells affected by the contaminants. At the same time, rapid small-scale column testing was conducted on the same GAC and alternative media systems at bench scale using groundwater from various basin wells. Because of its speed, this method enables comparisons of media performance for different local waters. The OCWD released a report on its website summarizing the test results in June.

All the various adsorbents were found to remove PFAS sufficiently to meet California’s water quality guidelines, Plumlee says. “Completing the study gave us a lot of confidence we can remove PFAS all the way down to nondetect levels,” she says. “Confirming that was important.”

Another “significant outcome” of the study “was seeing how different the life of the media can be,” Plumlee says. “That really affects your O&M costs because if you are removing the PFAS but (the adsorbent) only lasts for so long, you have to replace the adsorbent with fresh material more frequently. That drives O&M costs in a pretty dramatic way.”

Because new adsorbents are routinely introduced to the market, the OCWD will continue to evaluate various media regarding their ability to remove PFAS, Plumlee says. “For a project as large as ours, it makes sense,” she says. “We want to understand if we can save our water retailers and ourselves some cost by possibly identifying a superior product.”

Other new treatment facilities

The next of the OCWD’s treatment facilities to go online will be that of the Yorba Linda Water District. The first three treatment systems, comprising six vessels, are expected to begin operations in early November, Olsen says. “We’re staggering the startup sequence,” he notes. The treatment plant will consist of 11 vessel systems, for a total of 22 vessels, making the Yorba Linda facility the largest PFAS treatment system in the country. 

Construction has begun on PFAS treatment systems for three other retail water providers: the Serrano Water District, the city of Garden Grove, and the city of Orange. Design work is underway for treatment facilities slated for six other providers: the East Orange County Water District, the city of Fullerton, the Golden State Water Co., the Irvine Ranch Water District, the city of Santa Ana, and the city of Tustin.